Planets align for April viewing

Posted: Sunday, April 05, 2009

Days are getting longer and nights are getting shorter. We're also leaving the freezing cold behind. As we all love winter's benefits, we surely regret that our beloved starry skies will take a back seat soon. Therefore, after this article, see you again in August or September.

Graphic Courtesy Andy Veh
Graphic Courtesy Andy Veh

But at least we get some nice views for a good-bye. With Daylight Saving Time having started, it doesn't get dark until 10 p.m. or even later. Therefore, the diagram shows the western sky around 11 p.m. toward the end of April. This late in the season, many of the brilliant stars of winter are either gone or hard to detect. Therefore, look early in the month in the west for Sirius and Orion with Betelgeuse and Rigel, Aldebaran and the Pleiades. Still visible all month are the twins Castor and Pollux in the middle of the diagram, Procyon below and left of middle, Capella in its pentagon of Auriga on the right and, having shifted from east to west throughout late winter are Leo with Regulus and Saturn nearby. The latter is actually of virtually the same brightness as these bright stars and thus blends in pretty good, so you would need my description or a starfinder to identify Saturn.

All five naked eye planets are visible in April, for the first time in quite some time.

Mercury can be spotted very low on the northwest horizon after sunset, from about 10:30 p.m. until almost midnight, between mid-April and the end of April. Mercury is the brightest object in this part of the sky, although Betelgeuse and Aldebaran are almost as bright. The speedy planet and the two Red Giant stars appear in a nearly horizontal line on the western horizon with Procyon, Pollux, Castor, and Capella hovering above them. Starting on April 25 and 26, the crescent moon joins Mercury and the planet is moving ever closer toward the Pleiades. If we have clear skies on the Kenai and an unobstructed view toward the west (Mount Redoubt) and northwest (Mount Spurr), we should be able to see that spectacle.

Up all night is Saturn. Look for a large triangle of bright stars about 20 to 45 degrees above the southern horizon (in the evening). Those are Leo's Regulus on the right, Virgo's Spica on the left, and Bootes' Arcturus on the upper left. They play host to an intruder, Saturn, of similar brightness as the stars are. Until the wee hours that triangle with Saturn has moved toward the western horizon.

The other planets can be seen early in the morning, around 6 a.m., very low on the east to southeast horizon: from left to right they are Mars, Venus, even Uranus, and at a distance Neptune and Jupiter. The view from Alaska isn't favorable at all because from our latitudes it seems that those planets are hugging the horizon while the sky is getting brighter. Again, with an unobstructed view, this time toward the east, i.e. the Kenai mountains, one should spot very bright Venus (as we did all winter long in the evening skies) and Jupiter, and perhaps Mars can be seen as well. Uranus and Neptune would need binoculars but being so close to the horizon during almost daylight will render them invisible.

By the way, Venus may be the only bright celestial object visible during summer. But you'd have to try after 3 a.m., looking northeast.

Andy Veh is an associate professor of physics and mathematics at Kenai Peninsula College.

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